1. The Technical Field
This invention relates to improvements in engines and in engine components. The invention particularly relates to engines of the scotch yoke type and to components therefor.
2. The Prior Art
In a first aspect, the present invention deals with a development of an aspect of one of the inventions disclosed in International Patent Application No. PCT/AU00/00281. The invention in that disclosure related to a fluid device which included a crank having a big end with its axis orbiting around a main axis. Connecting means was rotatably mounted on the big end axis. At least one piston, being mounted for reciprocal motion in a cylinder along a piston axis, had piston guide means engaging engagement means on the connecting means. Also included was at least one restricting means for constraining the piston to move along the piston axis. In a preferred embodiment, as the crank mechanism rotated, the restricting means extended into the swept volume of the crank, projected along the main axis of the crank.
In the original invention as disclosed in PCT/AU00/00281, the piston guide means was commonly a surface which slidably engaged another surface, often complementary, on the connecting means. The restraining means was conveniently parallel to the piston axis and was described as extending into the swept volume of the crank mechanism, at least when the piston was at bottom dead center.
In a second aspect, the present invention deals with the manufacture of components suitable for use in connection with the scotch yoke devices in PCT/AU00/00281, as well as other forms of scotch yoke engine, and also in connection with the first aspect of the present invention.
It is possible to make the components of the inventions referred to from traditional materials, especially, in many cases, aluminum alloy. However, more recently inventions have been made with a view to manufacturing pistons from carbon-carbon material. There are significant advantages in that carbon-carbon components can have a higher melting point than aluminum alloy, for example and may retain room temperature strength to higher temperatures. They can be made lighter than aluminum components and have an extremely low co-efficient of thermal expansion.
Imported herein by reference is the content of the following US patent specifications dealing with carbon-carbon technology: U.S. Pat. Nos. 4,683,809, 4,909,133, 5,900,193 and 6,029,346 and 6,148,785.
U.S. Pat. No. 4,683,809 is concerned with the manufacture of a carbon-carbon piston involving inserting precursor fibers in a mat or random fiber orientation in a closed die, pyrolizing the precursor fibers, impregnating them with a carbonaceous resin system, stretching the precursor fiber prior to or during stabilization, stabilizing the material by heating the fiber in air, carbonizing the material by slowly heating the fiber in an inert atmosphere and graphitizing the fibers by raising the temperature to a desired beat treatment temperature. The piston can be fitted to a cylinder by lapping so as to precisely fit the bore of the cylinder. The piston may be constructed without piston grooves and without reinforcing material. The piston crown area may be reinforced with unidirectional fibers or cloth.
U.S. Pat. No. 4,909,133 discloses an improvement over the invention in U.S. Pat. No. 4,683,809, in which the crown, side wall, skirt and inner surfaces of the piston are armed by a one piece, closed end, single knitted fiber structural shape. It is claimed that a knitted fiber architecture, which enables the fiber directions to be controllable, results in increased strength properties, compared to cloth or mat.
U.S. Pat. No. 5,900,193 is concerned with a method of making carbon-carbon composite pistons by stacking carbon fiber laminae, prepregnated with a carbonaceous resin, over male mandrels to form a laminated composite billet, compressing female mandrels into the laminated composite billet to form a mould assembly, heating the laminated composite billet in the mould assembly to cure the carbonaceous resin, pyrolizing the composite billet to carbonize it, reimpregnating the carbonized composite billet with additional carbonaceous resin, repyrolizing to further density the billet and coring piston blanks, each with a crown and complete piston skirt surface, from the densified billet. The machined blanks can then be machined to final dimensions. The carbon fiber laminae may be woven carbon fabrics, unidirectional car fibers or directionally oriented to tailor structural and thermal properties. Optionally, ring grooves may be machined into the pistons. As an additional option, the crown and skirt surfaces of the piston blanks may be sealed, for example, with a ceramic coating or a metallic coating.
Further modifications are disclosed in U.S. Pat. No. 6,029,346.
Still further modifications are disclosed in U.S. Pat. No. 6,148,785.
The second aspect of this invention is concerned with improvements in making components of scotch yoke devices, including those disclosed in PCT/AU00/00281. In one particular aspect, the present invention is concerned with making a combined piston and connecting rod or connecting means using carbon-carbon composite or other fiber composite.